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65 lines
1.5 KiB
Markdown
65 lines
1.5 KiB
Markdown
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[buccen `$%` %bccn](#bccn)
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==========================
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Tagged union
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`$%` is a tile rune that produces a [`%kelp`](), the tile of the
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discriminated union. `$%` takes a list of lines which are labeled cases,
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called fronds, closed by `==`. Commonly used for pattern matching.
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Produces
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--------
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[Twig](): `[%kelp p=[i=line t=(list line)]]`
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Sample
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------
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`p` is a [`++list`]() of [`++line`]()s.
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Tall form
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---------
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$% p
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q
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==
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Wide form
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---------
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None
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Irregular form
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--------------
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None
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Examples
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--------
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~zod/try=> $%([%& @p] [%| @t])
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<1.dhe [* @n <246.qra 41.uuw 374.glo 100.rip 1.ypj %164>]>
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~zod/try=> *$%([%& @p] [%| @t])
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[%.y ~zod]
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~zod/try=> :type; *$%([%& @p] [%| @t])
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[%.y ~zod]
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{[%.y @p] [%.n @t]}
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~zod/try=> :type; *(each ,@p ,@t)
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[%.y p=~zod]
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{[%.y p=@p] [%.n p=@t]}
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~zod/try=> $%(~ [%a 1])
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~ <syntax error at [1 13]>
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~zod/try=> $%([%~ ~] [%a 1])
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<1.yck [* @n <246.qra 41.uuw 374.glo 100.rip 1.ypj %164>]>
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~zod/try=> *$%([%~ ~] [%a 1])
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[~ ~]
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++ foot $% [%ash p=twig] :: dry, geometric
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[%elm p=twig] :: wet, generic
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[%oak ~] :: XX not used
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[%yew p=(map term foot)] :: XX not used
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==
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In `++foot`, `$%` creates a list of possible cases. That is, a `++foot`
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can be either `%ash`, `%elm`, `%oak` or `%yew`.
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